The lower alcohols tend to form azeotropic solution with water which makes the separation challenging. The current work primarily focuses on the synthesis and application of a menthol-based hydrophobic deep eutectic solvent (DES) for the removal of lower alcohols from its aqueous solutions. The DES is synthesized by the addition of DL-menthol and lauric acid (dodecanoic acid) with a molar ratio of 2:1. Liquid−liquid equilibria (LLE) experiments are then performed to evaluate the performance of the synthesized DES for the extraction of lower alcohols such as ethanol, 1propanol, and 1-butanol. LLE corresponding to the pseudo ternary systems of lower alcohols (1-butanol, ethanol, and 1propanol) + hydrophobic DES + water are measured at T = 303.15 K and p = 1 atm. The composition of the tie lines were evaluated using 1 H NMR analysis for both extract and raffinate phases. Thereafter, the extraction efficiency of the DES is analyzed and compared by determining the solute distribution coefficients and the selectivity values. Finally, the experimental LLE data for the systems were regressed using the excess Gibbs free energy model, namely the Non Random Two Liquid (NRTL). Further the predictions of the tie lines were also confirmed through the COnductor like Screening MOdel Segment Activity Coefficients (COSMO-SAC) model. The average root-meansquare deviations (RMSD) obtained were 0.01 and 0.07 for NRTL and COSMO-SAC model, respectively.

Deep Eutectic Solvents (DESs) are gaining more interest as low-cost extraction media. Looking at its vast opportunity, the current work explores the extraction of alcohols namely ethanol, 1-propanol, and 1butanol from the aqueous phase using two novel hydrophobic DES at 303.15 K and 1 atm. The preparation of DES possess a common HBA (Hydrogen Bond Acceptor) with a HBD (Hydrogen Bond Donor such as organic acids i.e., lauric acid and decanoic acid) at a certain proportion. Ratios of 2:1 and 1:1 were used for synthesizing menthol: lauric acid (DES-1) and menthol/decanoic acid (DES-2), respectively. The highest extraction efficiency of alcohols was observed in the presence of DES-1. Thereafter, atomistic molecular dynamics (MD) simulations have also been adopted to understand the extraction mechanism of alcohols from water using these DES. From MD simulations, the interaction energies, structural properties such as radial and special distribution functions, and dynamic properties such as self-diffusivity are computed. From the results of MD simulations, it was inferred that menthol or the HBA was playing a vital role in the extraction of alcohols as compared lauric acid or decanoic acid. Furthermore, a process flow sheet was conceptualized for the separation and recycling of both DES and alcohol using ASPEN plus. It yielded a 99.7% and 98.3% recovery of DES and alcohol, respectively.

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